The infrared sensor has been widely used in the sanitary equipment, such as automatic sensing faucet, automatic flush urinal, flush facilities of the toilet, toilet seat having the hot water sprayer, hand dryer, toilet having the fan providing hot blast, etc.
Most of traditional infrared sensors adopt the active sensing method, i.e. the infrared emitter emits the infrared light with certain wavelength, and then the infrared receiver receives the infrared light after the reflection of the human body, further the infrared sensor judges the intensity of the reflected signals to realize the automatic sensing and judging. However, the infrared sensor could not complete the automatic sensing and judging if the target has low reflectivity to infrared light (for example, the black clothing, hair, etc.). There is only few infrared light could be received by the infrared receiver after the infrared light from the infrared emitter was reflected by such matter. The intensity of the reflected signals is not strong enough, so that the above infrared sensor fails to judge whether there is a target existing in the sensing area.
To solve the above-mentioned problem of induction malfunction in the traditional infrared sensing sanitary ware, the Position Sensitive Detector (PSD) is introduced to the automatic operation for sanitation and bathroom. Shown as FIG. 9, the PSD sensor is a kind of photoelectric apparatus which is sensitive to the position of the incident light. When the incident light irradiates on the different position of the photosensitive surface of the PSD, the PSD will send out the different electrical signal. Using the triangulation principle, the PSD can accurately survey the distance to realize the auto-induction judgment. Shown as FIG. 9, the light from the light source irradiates on the surface of the detected target after focused by the lens LI. The reflected light is focused onto the one-dimensional PSD by the lens L2 and forms a luminous spot. If the distance between the center of the lens L1 and the center of the lens L2 is “b”, the distance from the lens L2 to the surface of the PSD is “f’, the distance between the luminous spot focused on the surface of the PSD and the center of the lens L2 is “x”, the detected distance DIS can be expressed as: DIS=bf/x according to the principle of the similar triangles PAB and BCD. Therefore, so long as the value of the distance between the luminous spot focused on the surface of the PSD and the center of the lens L2 “x” is surveyed, the detected distance DIS can be determined.
When the distances of the detected target body fall into the pre-determined range, the distance detection induction device will control the sanitary fittings to work. Because the distance detection induction device achieves the purpose of the auto-induction by the way of judging the distance between the target and the distance detection induction device, not by the way of judging the intensity of the emitting signal, the problem of the induction malfunction caused by weak reflected signal in the traditional infrared sensing devices is solved.
However, it is necessary that the components of the distance detection induction device have higher positioning precision, therefore, so how to ensure the positioning precision of the device need to be solved.